Synergetic Effect of β-Cyclodextrin and Its Simple Carbohydrate Substituents on Complexation of Folic Acid and Its Structural Analog Methotrexate

Folic acid (FA) and its structural analog, anticancer medicine methotrexate (MTX), are known to form host/guest complexes with native cyclodextrins, of which the most stable are formed with the medium-sized β-cyclodextrin. Based on our research, proving that simple sugars (D-glucose, D-galactose, and D-mannose) can form adducts with folic acid, we envisioned that combining these two types of molecular receptors (cyclodextrin and simple carbohydrates) into one may be beneficial for the complexation of FA and MTX. We designed and obtained host/guest inclusion complexes of FA and MTX with two monoderivatives of β-cyclodextrin-substituted at position 6 with monosaccharide (glucose, G-β-CD) and disaccharide (maltose, Ma-β-CD). The complexation was proved by experimental (NMR, UV-vis, IR, TG, DSC) and theoretical methods. We proved that derivatization of β-cyclodextrin with glucose and maltose has a significant impact on the complexation with FA and MTX, as the addition of one glucose subunit to the structure of the receptor significantly increases the value of association constant for both FA/G-β-CD and MTX/G-β-CD, while further extending a pendant chain (incorporation of maltose subunit) results in no additional changes.